LED light engine features

Abstract

A lighting engine, system and method of fabrication are described. The engine contains a chassis having a side wall and bottom surface that define a cavity. A recess is formed in the bottom surface. A flexible printed circuit (FPC) is on the side wall and LEDs are mounted on the FPC to emit light toward a center of the cavity. A light guide positioned within the cavity receives light emitted by the LEDs through an edge of the light guide. A gasket disposed within the recess is in contact with a first surface of the light guide. A reflector within the cavity is adjacent to a second surface of the light guide opposite the first surface of the light guide. A backplate is attached to the chassis and configured to seal the cavity. Other apparatuses, systems, and methods are also disclosed.

What is claimed is: 
     
       1. A lighting system comprising:
 a chassis having a side wall and bottom surface, the side wall and the bottom surface defining a cavity, with a recess formed in the bottom surface; 
 a flexible printed circuit (FPC) disposed on the side wall; 
 light emitting diodes (LEDs) mounted on the FPC, the LEDs positioned to emit light toward a center of the cavity; 
 a light guide positioned within the cavity to receive light emitted by the LEDs through an edge of the light guide; 
 a gasket disposed within the recess, the gasket being in contact with a first surface of the light guide and disposed closer to the center of the cavity than the LEDs; 
 a reflector within the cavity adjacent to a second surface of the light guide opposite the first surface of the light guide; 
 a backplate attached to the chassis and configured to seal the cavity; and 
 a white reflective sheet disposed between the reflector and the backplate, the white reflective sheet having a diameter larger than that of the reflector. 
 
     
     
       2. The lighting system of  claim 1 , further comprising:
 spacers attached to the chassis between the reflector and the backplate. 
 
     
     
       3. The lighting system of  claim 2 , wherein:
 the backplate is in contact with the spacers, and 
 the backplate comprises a groove is configured such that, if the spacers were absent, the backplate would assert pressure on the reflector proximate to an edge of the reflector. 
 
     
     
       4. The lighting system of  claim 2 , wherein:
 a protrusion in the bottom surface of the chassis that forms an outer wall of the recess is configured such that, if the gasket was absent, the protrusion would assert pressure on the light guide proximate to the edge of the light guide. 
 
     
     
       5. The lighting system of  claim 4 , wherein:
 the protrusion is disposed more proximate to the LEDs than the groove is disposed to the LEDs. 
 
     
     
       6. The lighting system of  claim 2 , wherein:
 the spacers comprise a central spacer disposed at an approximate center of the reflector and an approximate center of the backplate and distributed spacers disposed at about symmetric locations farther from the center of the reflector and the center of the backplate than the central spacer. 
 
     
     
       7. The lighting system of  claim 6 , wherein:
 the central spacer is formed in a circular disc shape and the distributed spacers are formed in a semicircular disc shape having a flat side opposing the central spacer. 
 
     
     
       8. The lighting system of  claim 1 , wherein the reflector covers the second surface of the light guide, an edge of the reflector is more proximate to the FPC than the edge of the light guide. 
     
     
       9. The lighting system of  claim 1 , wherein the reflector is disposed in the cavity and has a diameter to provide a clearance distance of 1.6 mm from the FPC. 
     
     
       10. The lighting system of  claim 1 , further comprising:
 a dispersive pattern configured to prevent generation of Moiré fringes disposed on the second surface of the light guide, and 
 a transparent adhesive disposed on the second surface of the light guide to attach the reflector and the light guide. 
 
     
     
       11. The lighting system of  claim 1 , further comprising:
 locator pins disposed within recesses formed in the bottom surface of the chassis, the light guide comprising a plurality of slots formed therein and configured to receive the locator pins to limit thermal displacement of the light guide towards the LEDs. 
 
     
     
       12. The lighting system of  claim 11 , wherein:
 the chassis comprises a protrusion, 
 the sidewall is an inner wall of the protrusion, and 
 the FPC has a leg that extends, for electrical contact, over a top of the protrusion to an outer wall on an opposite side of the protrusion as the inner wall. 
 
     
     
       13. A lighting engine comprising:
 a metal chassis having a side wall and bottom surface, the side wall and the bottom surface defining a cavity having a circular cross-section; 
 a flexible printed circuit (FPC) disposed on the side wall; 
 light emitting diodes (LEDs) mounted on the FPC separated from the bottom surface by a predetermined distance, the LEDs positioned to emit light toward a center of the cavity; 
 a substantially transparent light guide positioned within the cavity to receive light emitted by the LEDs through an edge of the light guide, the light guide having a first surface opposing the bottom surface of the chassis; 
 a reflector within the cavity adjacent to a second surface of the light guide opposite the first surface of the light guide; 
 a reflective material disposed between the reflector and the FPC,
 the reflective material comprising a reflective tape disposed between the reflector and the FPC, over an edge of the reflector, and between the reflector and a backplate, 
 the reflective tape attached to the light guide, the edge of the reflector, and a surface of the reflector opposing the backplate, 
 the reflective tape terminating at the edge of the light guide; and 
 
 a secondary reflective material disposed on the reflective tape on the light guide and between the reflective tape and the FPC. 
 
     
     
       14. The lighting engine of  claim 13 , wherein:
 a dispersive pattern configured to prevent generation of Moiré fringes is disposed on the second surface of the light guide. 
 
     
     
       15. A method of fabricating a lighting system, the method comprising:
 attaching a flexible printed circuit (FPC) to a side wall of a cavity, the cavity having a circular cross-section, in a metal chassis, the FPC having light emitting diodes (LEDs) mounted thereon such that the LEDs are positioned to emit light toward a center of the cavity; 
 inserting a gasket into a recess formed in a bottom surface of the cavity; 
 positioning a substantially transparent light guide in the cavity such that a first surface of the light guide contacts the gasket and an edge of the light guide opposes the LEDs and is configured to receive light emitted by the LEDs; 
 inserting a reflector in the cavity adjacent to a second surface of the light guide such that the reflector entirely covers the light guide and is configured to reflect substantially all light incident on the reflector from the light guide back toward the light guide; 
 positioning a white reflective sheet on the reflector, the white reflective sheet having a diameter larger than that of the reflector and 
 attaching a backplate to the chassis to seal the cavity, the white reflective sheet positioned between the reflector and the backplate.